The vast majority of models of treatment outcome and addiction relapse have been formulated on adult populations with only modest consideration of major developmental transitions or psychiatric factors which are salient issues for youth. The present proposal seeks 18 months of funding to test developmentally sensitive models of drug and alcohol relapse and seeks to answer two main questions in youths and adults: 1) What are the relationships between depression diagnoses, symptoms, and context of first substance use (SU) after treatment?, 2) How does depression comorbidity affect the relationship between drug-related coping self-efficacy and length of time to first use after treatment? Data will be drawn from an existing sample of youth and adults diagnosed with at least one substance use disorder (SUD), some of whom have a comorbid depression diagnosis (SUD/DEP). Youth and adults were interviewed during inpatient substance abuse and mental health treatment and followed monthly for one year after treatment to gather detailed information on patterns, context, and severity of SU. Multigroup path analysis will be used to compare two sets of hypothesized models in youths and adults that test the following relationships: 1) depression and context of first SU episode; and 2) depression, self-efficacy, and length of time to relapse. Results will aide in understanding how depression comorbidity affects the cognitive process of relapse throughout development. [unreadable] [unreadable] [unreadable]